HP 30b - Business Professional Calculator - Mathematical Calculations; Mathematical Functions; Number Entry and Display

Getting Started 13
One way to calculate this problem is to key in the numbers and operations
within the parentheses first, followed by the operation outside of the
parentheses. See Table 1-2.
Table 1-2
Keys Display and Description
3I
4+
Inputs the numbers and the operation in the first set of
parentheses. Intermediate results are displayed. Note the
(+) and (RPN) annunciators.
5I
6+
Inputs the numbers and the operation in the second set of
parentheses. Intermediate results are displayed. Note
the (+) annunciator.
*
Finishes the operation and displays the results.